/*
===========================================================================
Copyright (C) 1997-1998  Andrew Tridgell

This file is part of XreaL source code.

XreaL source code is free software; you can redistribute it
and/or modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2 of the License,
or (at your option) any later version.

XreaL source code is distributed in the hope that it will be
useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with XreaL source code; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
===========================================================================
*/
#include "q_shared.h"



struct mdfour
{
	uint32_t        A, B, C, D;
	uint32_t        totalN;
};


/* NOTE: This code makes no attempt to be fast!

   It assumes that a int is at least 32 bits long
*/

static struct mdfour *m;

#define F(X,Y,Z) (((X)&(Y)) | ((~(X))&(Z)))
#define G(X,Y,Z) (((X)&(Y)) | ((X)&(Z)) | ((Y)&(Z)))
#define H(X,Y,Z) ((X)^(Y)^(Z))
#define lshift(x,s) (((x)<<(s)) | ((x)>>(32-(s))))

#define ROUND1(a,b,c,d,k,s) a = lshift(a + F(b,c,d) + X[k], s)
#define ROUND2(a,b,c,d,k,s) a = lshift(a + G(b,c,d) + X[k] + 0x5A827999,s)
#define ROUND3(a,b,c,d,k,s) a = lshift(a + H(b,c,d) + X[k] + 0x6ED9EBA1,s)

/* this applies md4 to 64 byte chunks */
static void mdfour64(uint32_t * M)
{
	int             j;
	uint32_t        AA, BB, CC, DD;
	uint32_t        X[16];
	uint32_t        A, B, C, D;

	for(j = 0; j < 16; j++)
		X[j] = M[j];

	A = m->A;
	B = m->B;
	C = m->C;
	D = m->D;
	AA = A;
	BB = B;
	CC = C;
	DD = D;

	ROUND1(A, B, C, D, 0, 3);
	ROUND1(D, A, B, C, 1, 7);
	ROUND1(C, D, A, B, 2, 11);
	ROUND1(B, C, D, A, 3, 19);
	ROUND1(A, B, C, D, 4, 3);
	ROUND1(D, A, B, C, 5, 7);
	ROUND1(C, D, A, B, 6, 11);
	ROUND1(B, C, D, A, 7, 19);
	ROUND1(A, B, C, D, 8, 3);
	ROUND1(D, A, B, C, 9, 7);
	ROUND1(C, D, A, B, 10, 11);
	ROUND1(B, C, D, A, 11, 19);
	ROUND1(A, B, C, D, 12, 3);
	ROUND1(D, A, B, C, 13, 7);
	ROUND1(C, D, A, B, 14, 11);
	ROUND1(B, C, D, A, 15, 19);

	ROUND2(A, B, C, D, 0, 3);
	ROUND2(D, A, B, C, 4, 5);
	ROUND2(C, D, A, B, 8, 9);
	ROUND2(B, C, D, A, 12, 13);
	ROUND2(A, B, C, D, 1, 3);
	ROUND2(D, A, B, C, 5, 5);
	ROUND2(C, D, A, B, 9, 9);
	ROUND2(B, C, D, A, 13, 13);
	ROUND2(A, B, C, D, 2, 3);
	ROUND2(D, A, B, C, 6, 5);
	ROUND2(C, D, A, B, 10, 9);
	ROUND2(B, C, D, A, 14, 13);
	ROUND2(A, B, C, D, 3, 3);
	ROUND2(D, A, B, C, 7, 5);
	ROUND2(C, D, A, B, 11, 9);
	ROUND2(B, C, D, A, 15, 13);

	ROUND3(A, B, C, D, 0, 3);
	ROUND3(D, A, B, C, 8, 9);
	ROUND3(C, D, A, B, 4, 11);
	ROUND3(B, C, D, A, 12, 15);
	ROUND3(A, B, C, D, 2, 3);
	ROUND3(D, A, B, C, 10, 9);
	ROUND3(C, D, A, B, 6, 11);
	ROUND3(B, C, D, A, 14, 15);
	ROUND3(A, B, C, D, 1, 3);
	ROUND3(D, A, B, C, 9, 9);
	ROUND3(C, D, A, B, 5, 11);
	ROUND3(B, C, D, A, 13, 15);
	ROUND3(A, B, C, D, 3, 3);
	ROUND3(D, A, B, C, 11, 9);
	ROUND3(C, D, A, B, 7, 11);
	ROUND3(B, C, D, A, 15, 15);

	A += AA;
	B += BB;
	C += CC;
	D += DD;

	for(j = 0; j < 16; j++)
		X[j] = 0;

	m->A = A;
	m->B = B;
	m->C = C;
	m->D = D;
}

static void copy64(uint32_t * M, byte * in)
{
	int             i;

	for(i = 0; i < 16; i++)
		M[i] = (in[i * 4 + 3] << 24) | (in[i * 4 + 2] << 16) | (in[i * 4 + 1] << 8) | (in[i * 4 + 0] << 0);
}

static void copy4(byte * out, uint32_t x)
{
	out[0] = x & 0xFF;
	out[1] = (x >> 8) & 0xFF;
	out[2] = (x >> 16) & 0xFF;
	out[3] = (x >> 24) & 0xFF;
}

void mdfour_begin(struct mdfour *md)
{
	md->A = 0x67452301;
	md->B = 0xefcdab89;
	md->C = 0x98badcfe;
	md->D = 0x10325476;
	md->totalN = 0;
}


static void mdfour_tail(byte * in, int n)
{
	byte            buf[128];
	uint32_t        M[16];
	uint32_t        b;

	m->totalN += n;

	b = m->totalN * 8;

	Com_Memset(buf, 0, 128);
	if(n)
		Com_Memcpy(buf, in, n);
	buf[n] = 0x80;

	if(n <= 55)
	{
		copy4(buf + 56, b);
		copy64(M, buf);
		mdfour64(M);
	}
	else
	{
		copy4(buf + 120, b);
		copy64(M, buf);
		mdfour64(M);
		copy64(M, buf + 64);
		mdfour64(M);
	}
}

static void mdfour_update(struct mdfour *md, byte * in, int n)
{
	uint32_t        M[16];

	m = md;

	if(n == 0)
		mdfour_tail(in, n);

	while(n >= 64)
	{
		copy64(M, in);
		mdfour64(M);
		in += 64;
		n -= 64;
		m->totalN += 64;
	}

	mdfour_tail(in, n);
}


static void mdfour_result(struct mdfour *md, byte * out)
{
	m = md;

	copy4(out, m->A);
	copy4(out + 4, m->B);
	copy4(out + 8, m->C);
	copy4(out + 12, m->D);
}

static void mdfour(byte * out, byte * in, int n)
{
	struct mdfour   md;

	mdfour_begin(&md);
	mdfour_update(&md, in, n);
	mdfour_result(&md, out);
}

//===================================================================

unsigned Com_BlockChecksum(const void *buffer, int length)
{
	int             digest[4];
	unsigned        val;

	mdfour((byte *) digest, (byte *) buffer, length);

	val = digest[0] ^ digest[1] ^ digest[2] ^ digest[3];

	return val;
}
